1. Field of the Invention
The present invention relates to a vehicular control device which detects the operation of an accelerator device (such as an accelerator pedal or a throttle valve) performed by a driver and controls an electric motor or an internal combustion engine of a vehicle responsive to the detected operation of the accelerator device.
2. Related Art
Japanese Patent Application Laid-Open No. Hei 5-99058 discloses that, in an electric motor vehicle, two accelerator sensors are provided. The accelerator sensors detect the amount that an accelerator pedal is depressed and generate output voltages corresponding to the detected depression of the accelerator pedal. The electrical motor is controlled based on a lower output voltage ACL (=min (ACL1, ACL2)) of the two output voltages ACL1, ACL2 generated by the accelerator sensors.
The accelerator sensor can be formed by a Hall element. The Hall element magnetically detects the depression of the accelerator pedal and changes the magnetically-detected amount into a voltage signal. The voltage signal generated by the Hall element is fed to a signal processing circuit. The signal processing circuit has a standard voltage generating circuit which generates a standard voltage. The standard voltage is set to an intermediate voltage value between maximum and minimum voltages that the signal processing circuit can generate. The signal processing circuit amplifies the voltage signal from the Hall element. Accordingly, the signal processing circuit generates a maximum voltage when the accelerator pedal is fully depressed and generates a minimum voltage when the accelerator pedal is not depressed.
When moisture, dust or the like affects the signal processing circuit, the signal processing circuit may malfunction. In this case, the signal processing circuit may generate an output voltage fixed at an intermediate voltage value, or the relationship between the output voltage and the change in the accelerator pedal depression, i.e. the sensitivity of the accelerator sensor, abnormally increases or decreases.
For example, in the case where an output voltage ACL1 is fixed at an intermediate voltage value as shown in FIG. 41A, the selected output voltage ACL follows the output voltage ACL1 after the depression of the accelerator pedal reaches half-way to the fully depressed position. Accordingly, even if a driver depresses the accelerator pedal, the vehicle does not accelerate responsive to the operation.
In the case where the change of the output voltage ACL1 caused by a change of the accelerator pedal depression abnormally increases as shown in FIG. 41B, the selected output voltage ACL follows the output voltage ACL1 until the output voltage ACL1 goes beyond a normal output voltage ACL2. Accordingly, even if a driver begins to depress the accelerator pedal, since the output voltage ACL1 is zero until the accelerator pedal is depressed to a certain amount, a vehicle cannot be accelerated. After that, since the output voltage ACL1 is rapidly boosted, the vehicle suddenly accelerates. Therefore, the driver can sense that the acceleration operation is abnormal.
Finally, in the case where the change of the output voltage ACL1 caused by a change of the accelerator pedal depression abnormally decreases as shown in FIG. 41C, the selected output voltage ACL follows the output voltage ACL1 after the output voltage ACL1 goes below a normal output voltage ACL2. Accordingly, even if a driver depresses the accelerator pedal, the driver does not obtain a sufficient acceleration of the vehicle. The driver can sense abnormal operation in this case as well.
If only one accelerator sensor is provided for a vehicular control device and the signal processing circuit malfunctions, an abnormal output voltage will be used in the vehicular control device. Consequently, the vehicular control device cannot properly control the vehicle.